These files represent uncertainty surfaces accompanying the datasets
"Historical built-up areas (BUA) - gridded surfaces for the U.S. from 1810 to 2015"
"Historical built-up property locations (BUPL) - gridded surfaces for the U.S. from 1810 to 2015"
"Historical built-up property records (BUPR) - gridded surfaces for the U.S. from 1810 to 2015",
contained in the dataverse �HISDAC-US: Historical Settlement Data Compilation for the United States� 
(https://dataverse.harvard.edu/dataverse/hisdacus).

Reference:
Uhl, Johannes H.; Leyk, Stefan, 2020, "Uncertainty surfaces accompanying the BUPR, BUPL, and BUA gridded surface series",
https://doi.org/10.7910/DVN/T8H5KF, Harvard Dataverse.

The gridded surface in NBY.tif represents a binary grid, flagging grid cells (value 1) that contain built-up property records, 
but do not contain any temporal information (i.e., built year information). These grid cells are called no-built-year (NBY) cells.
This surface allows for excluding grid cells without temporal information 
from data analysis based on the BUPR, BUPL, and BUA series.

Abbreviations and explanations:
BUA:			Built-up areas. Grid cells containing at least one built-up property in a given year.
BUPR:			Built-up property records. Individual built-up property records in ZTRAX, representing a building or building unit, depending on ownership situation.
BUPL:			Built-up property locations. Unique locations of built-up property records (i.e., buildings or building units), independent from ownership situation.

Data source: Zillow Transaction and Assessment Dataset (ZTRAX) (c) Zillow Inc.
Spatial resolution: 250m
Coordinate reference system:
USA Contiguous Albers Equal Area Conic USGS version (SR-ORG:7480)
https://spatialreference.org/ref/sr-org/usa_contiguous_albers_equal_area_conic_usgs_version-2/
Proj4: +proj=aea +lat_1=29.5 +lat_2=45.5 +lat_0=23.0 +lon_0=-96 +x_0=0 +y_0=0 +ellps=GRS80 +datum=NAD83 +units=m +no_defs

Contact:
Stefan Leyk
Department of Geography
University of Colorado Boulder
GUGG 110, 260 UCB 
Boulder, CO 80309-0260, United States of America
stefan.leyk@colorado.edu